This invention relates to an apparatus for generating a vacuum.
A vacuum pump such as a liquid-ring pump operates with a working fluid and is driven by an electric motor. The vacuum pump is followed by a preseparator which functions as a first stage for separating the working fluid from the gaseous mixture at the output of the liquid-ring pump. The working fluid separated out in the preseparator is fed via a liquid cooler back to the vacuum pump, while a gaseous component still loaded with a residue of the working fluid is fed to a fine separator at an output of the preseparator. A return line is connected between the fine separator and the liquid-ring pump for returning thereto fluid separated out in the fine separator.
Such as vacuum generating device is described in the journal "Fluid," October 1982, at page 58. In this device, the gaseous component leaving the preseparator is conducted over a fine filter which is disposed in a chamber adjacent to the preseparator.
It is known that the efficiency or effectiveness of the separation process depends to a high degree upon temperature, particularly when the working fluid is oil. A substantially better separation of the oil from the gas being pumped is achieved at lower oil temperatures.
Accordingly, in a compressed-air generator described in German Patent Document (Deutsche Offenlequncsschrift) No. 26 36 493, a cooler is arranged between the compressor and the preseparator for achieving a better separation of the working fluid (oil) from the compressed air: the gas-oil mixture leaving the compressor is cooled prior to arriving at the preseparator. In the process, the oil is cooled to relatively low temperatures, which requires a large heat exchanger or cooler.
It is to be noted tnat in a vacuum generating device, low temperatures of tne working fluid fed back into the vacuum pump are undesirable inasmuch as they cause condensation of the moisture contained in the intake air of the vacuum pump.
An object of the present invention is to provide an improved vacuum generating apparatus of the type generally described above.
Another, more particular, object of the present invention is to provide such a vacuum generating apparatus in which the degree of liquid separation is substantially improved by cooling and which there is little or no condensation of moisture within the pump and the preseparator from the gas being pumped.
Further object of tne present invention is to provide such a vacuum generating apparatus which has a minimum number of mechanical devices to achieve the separation and cooling.
Yet another object of the present invention is to provide such a vacuum generating apparatus which occupies a relatively small amount of space.